The development of optical transmission technology reveals a trend towards a higher rate on a single channel (e.g. a rate of 400G/1T on a single channel), a higher spectrum efficiency and a high-order modulation format, thus, the most definite and important development direction of optical transmission technology still lies in increasing transmission rate. High-speed transmission confronts a lot of limitations mainly in two aspects: aspect 1: optical transmission technology is developing towards convergence transmission of high spectrum efficiency and high-speed service interface transmission, if spectrum efficiency cannot be improved further, then the convergence of low speed services to a high-speed channel for transmission is not much meaningful, nonetheless, there may be a high-speed Ethernet interface at a client side, thus, the transmission of a high-speed interface still needs to be taken into consideration, and 400G will be the critical point of the limit of spectrum efficiency; aspect 2: as optical transmission technology is developing towards long-distance (long-span and multi-span) transmission, the use of a low-loss fiber and a low-noise amplifier, the shortening of spans and the application of other approaches, although capable of partly improving the Optical Signal-Noise Ratio (OSNR) of a system, cannot make a breakthrough, in addition, it is difficult to implement these approaches in engineering.
With the bandwidth of a bearer network required to be higher and higher, a beyond-100G technology becomes a solution to meet the requirement for higher bandwidth; the Wavelength Division Multiplexing (WDM) of the conventional 50 GHz fixed grid cannot provide a sufficient spectrum width to realize a beyond-100G technology, no matter a 400G technology or a 1T technology. In view of the defects of the fixed grid, a wider flexible grid is needed. In related art, the flexibility of beyond-100G multi-rate hybrid transmission and beyond-100G modulation format gives rise to different requirements on channel bandwidth, if a proper bandwidth is customized for each channel, then the bandwidth of a system can be fully used, thereby generating a flexible grid system. The requirement for an ultra high-speed WDM system brought by the demand for higher and higher bandwidth leads to a demand for a flexible grid technology; the introduction of the flexible grid technology creates spectrum fragmentations, it may occur that no continuous sufficiently wide spectrum can be provided to transmit a beyond-100G service, for example, a 1T Ethernet service, on an optical layer, thus, it is needed to inversely multiplex a 1T electrical container to a plurality of discontinuous spectrums for transmission, thereby improving spectrum efficiency and making the best use of fragmentations of spectrum. Optical devices using coherent reception technologies are developed which are capable of dynamically and correctly receiving optical signals according to configured information such as the received central frequency, spectrum width and modulation format.
No effective solution has been proposed to address the problem of how to effectively detect the misconnection of optical fibers after coherent reception technologies, including flexible grid, inverse multiplexing and optical devices, are introduced into related technologies.